UDS Diagnostics

Learn ISO 14229 diagnostics, ISO-TP, services, NRCs, timing and flashing.

What is UDS?

Diagnostic Tester Scan Tool UDS Application / diagnostic services

ISO-TP / CAN-TP Transport & segmentation CANIF / CAN Controller CAN interface & protocol handling CAN Physical / data-link access ECU Diagnostic Server + Application

UDS Diagnostic application protocol ISO-TP Transport layer CAN Network communication Transceiver Electrical interface CAN_H / CAN_L Differential physical bus

UDS is the diagnostic application layer. ISO-TP transports larger diagnostic payloads; CAN and the transceiver carry the information onto the physical bus. Exact AUTOSAR partitioning varies by ECU platform.

UDS Communication Architecture CAN_H CAN_L Differential physical bus Automotive ECU Diagnostic Server UDS Request & Response

Diagnostic Tester ECU / Diagnostic Server 10 03 Diagnostic Session Control • Extended session 50 03 50 = 10 + 0x40

7F 10 12 Negative response • Sub-function not supported 22 F1 90 22 = ReadDataByIdentifier • DID F190

62 F1 90 XX XX 62 = positive response • returned DID data UDS Message Format

SID10 Sub-function03 Data RecordParameters...

Example: 10 03 Response SID50 Sub-function03 Data Record...

Response SID = Request SID + 0x40 Negative SID7F Request SID22 NRC31

7F = negative response • 31 = Request Out Of Range Request 22 F1 90 → Response 62 F1 90 XX XX UDS Diagnostic Sessions 0x01 DEFAULT Normal operation 0x03 EXTENDED Expanded diagnostics 0x02 PROGRAMMING Flashing / programming ECU Diagnostic Server

S3 session timeout Tester Present 0x3E Security may protect operations Service availability is ECU/OEM dependent UDS Timing — P2, P2* and S3

Tester 22 F1 90 ECU 62 F1 90... P2: normal response time Tester 22 F1 90 ECU processing... 7F 22 78 P2*: extended processing after Response Pending 62 F1 90...

3E 00 3E 00 3E 00... S3: session timeout mechanism UDS Diagnostic Services — ISO 14229

Diagnostic Tester ↓ UDS ↓ ISO-TP ↓ CAN ↓ ECU ISO-TP — ISO 15765-2 1 • SINGLE FRAME 03 = SF + payload length 3 Tester → FIRST FRAME 10 xx...

ECU ← FLOW CONTROL 30 BS STmin Tester → CONSECUTIVE 1 21 AA BB CC Tester → CONSECUTIVE 2 22 11 22 33 Tester → CONSECUTIVE 3 23 55 66 77

PCI Protocol Control Information FS 00 CTS • 01 WAIT • 02 OVERFLOW BS Consecutive-frame block size STmin Minimum separation time SN CF sequence number 1…F, then wrap Back to CAN Diagnostics AUTOMOTIVE • DIAGNOSTICS • ISO 14229

Learn Unified Diagnostic Services from the diagnostic stack and request/response model to ISO-TP, services, NRCs, timing, ECU flashing and troubleshooting.

Diagnostics Track CAN → ISO-TP → UDS